Messages in this thread | | | Date | Thu, 15 Feb 2024 14:47:00 -0800 | From | Kees Cook <> | Subject | Re: [PATCH 1/2] wordpart.h: Helpers for making u16/u32/u64 values |
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On Thu, Feb 15, 2024 at 09:40:40PM +0100, Michal Wajdeczko wrote: > On 14.02.2024 23:09, Kees Cook wrote: > > On Wed, Feb 14, 2024 at 10:46:53PM +0100, Michal Wajdeczko wrote: > >> It is quite common practice to make u16, u32 or u64 values from > >> smaller words. Add simple helpers for that. > >> > >> Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com> > >> --- > >> v2: new macro names due to conflict with crypto/aria.h > >> explicit cast and truncation everywhere (Alexey) > >> moved to wordpart.h (Andy) > >> --- > >> Cc: Kees Cook <keescook@chromium.org> > >> Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com> > >> Cc: Alexey Dobriyan <adobriyan@gmail.com> > >> Cc: Jani Nikula <jani.nikula@intel.com> > >> --- > >> include/linux/wordpart.h | 32 ++++++++++++++++++++++++++++++++ > >> 1 file changed, 32 insertions(+) > >> > >> diff --git a/include/linux/wordpart.h b/include/linux/wordpart.h > >> index f6f8f83b15b0..8c75a5355112 100644 > >> --- a/include/linux/wordpart.h > >> +++ b/include/linux/wordpart.h > >> @@ -31,6 +31,38 @@ > >> */ > >> #define lower_16_bits(n) ((u16)((n) & 0xffff)) > >> > >> +/** > >> + * make_u16_from_u8 - make u16 value from two u8 values > >> + * @hi: value representing upper 8 bits > >> + * @lo: value representing lower 8 bits > >> + */ > >> +#define make_u16_from_u8(hi, lo) ((u16)((u16)(u8)(hi) << 8 | (u8)(lo))) > > > > Do we want to actually do type validation here? Right now it's just > > cast/truncating, which based on the version log is by design. Is silent > > truncation the right thing to do? > > note that even FIELD_PREP() is doing silent truncation and these macros > here could be treated as specialized/simplified variants of FIELD_PREP() > as alternate implementation can look like:
Also, isn't all of this endian-specific?
-- Kees Cook
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